Rotary driers



April 12, 1966 G. BOJNER ETAL 3,245,154

ROTARY DRIERS Filed July 10, 1962 s Sheets-Sheet 1 April 1966 e. BOJNER ETAL 3,245,154

ROTARY DRIERS Filed July 10, 1962 5 Sheets-Sheet 2 April 12, 1966 G. BOJNER ETAL 3,245,154

ROTARY DRIERS Filed July 10, 1962 3 Sheets-Sheet 3 United States Patent 3,245,154 ROTARY DRIERS Gustav Bojner and Gtista Bojner, both of Sveavagen 28-30, Stockholm, Sweden Filed July 10, 1962, Ser. No. 208,853 Claims priority, application Sweden, Aug. 17, 1961, 8,294/ 61 4 Claims. (Cl. 34-142) The invention relates to rotatable drums for drying and other heat-treatment or cooling of solid material in a fluent state, such as a pulverulent, granular or crystalline state, by exchange of heat between the solid material and a gaseous medium (for instance hot flue-gases or hot or cold air), said material and said medium passing axially through the drum in a co-current or counter-current relationship.

Generally such drums are equipped with screw-like feeding bars for feeding the fluent solid material axially through the drum. In addition they can be provided with lifting bars extending longitudinally Within the drum for lifting the fluent solid material during the rotation of the drum, the lifted material then falling down successively as the lifting bars move through their upper locations during the revolution. The object thereof is to improve the exchange of heat between the material and the gaseous medium. However, the lifted material falls down from the lifting bars always in approximately the same location of the bars during the revolution, in particular immediately before the highest point during the revolution when the bars are mounted radially, and therefore the falling material will pass only a smaller fraction of the transversal cross-section of the drum, while the remaining part of said cross-section is passed by the gaseous medium without contact between said medium and any material falling down.

For drying sugar in a granular state, it has been suggested to utilize finely toothed lifting bars, the very points of the teeth being bent upwards. In this known arrangement the toothed bars are mounted with such an angle against the circumference of the drum that essentially all lifted material falls down only near the highest point during the revolution. Although the triangular spaces between the teeth in practice possibly can allow some material to fall down before the highest point during the revolution, the major part of the material will fall'down through the central part of the transversal cross-section of the drum, whereby the gaseous medium on each side of this central part is not effectively utilized.

The object of the invention is to create a simple arrangement for allowing and securing a more uniform distribution of the falling material over the transversal crosssection and thus causing a more effective heat-exchange or drying in connection with the treatment of solid materials of different kinds in a fluent state, even of sticky nature or in slurry condition.

In the arrangement according to the invention, the drum is provided with bar-like lifting members having their free edge formed with spaced-apart tongues of considerable width in the longitudinal direction at their free edges, and these tongues are bent in the direction of rotation and along a line substantially coincident with the inner edge of the spaces between the tongues, said inner edge extending in the longitudinal direction of the barlike lifting member. The bending angle of the tongues Patented Apr. 12, 1966 is such that the tongues carry the lifted material with their entire surface beyond the highest point during the revolution and only thereafter allow this material to fall down, while the material carried by the sections of the lifting members opposite said spaces is allowed already before the highest point to fall down through these spaces which are relatively wide in the longitudinal direction. In this way one and the same lifting member will deliver material both before and after the highest point of the revolution, and on account of the great number of lifting members distributed over the circumference substantially the entire transversal cross-section of the drum or in any case the major part thereof will in operation be filled with falling material.

Due to the effective distribution of the falling material over the major part of the cross-section of the drum, the formation of dust in many cases will be rather great, and for this reason it"may be advantageous to omit the lifting bars over a distance before the discharge end of the drum, where a sector unit for dust separation is provided instead of lifting bars.

Other objects and features of the invention will appear from the following description when read in conjunction with the accompanying drawing, wherein one embodiment of the invention is illustrated by way of example, and in which:

FIG. 1 is a longitudinal cross-section of a drying drum together with an arrangement according to the invention.

FIGS. 2, 3, and 4 are corresponding transversal crosssections, taken along the lines IIII and IIIIII and IV-IV, respectively, in FIG. 1.

FIG. 5 is a cross-section through a lifting bar according to the preferred embodiment of invention.

FIG. 6 is a fractional plan of the lifting bar, as seen in the direction of the arrow VI in FIG. 5.

FIG. 7 is a cross-section through a lifting bar according to a modified embodiment.

FIG. 8 is a longitudinal cross-section of a drying drum representing a modified mounting of the lifting bars.

FIGS. 9 and 10 are corresponding transversal crosssections, taken along the lines IX-IX and XX, respectively, in FIG. 8.

The rotatable drum comprises the cylindrical shell 1 and the two annular end-walls 2. By means of the annular tracks 3 securely mounted on the shell, said drum is supported by two pairs of wheels 4 for rolling on the same, one of the wheels in each pair being driven. In operation the drum rotates in the direction of the arrow A (FIG. 3). The material to be treated in the drum (or several kinds of material to be mixed) is supplied through the stationary hopper 5. After the passage through the drum, the material is discharged through the stationary discharge chamber 6 which is provided with an outlet 6' directed downwards. The gaseous medium is supplied through the stationary inlet chamber 17, passes through the drum in the same direction as the material and escapes through the outlet 6" which is directed upwards.

The longitudinally extending lifting bars are indicated by 7. According to the invention, each lifting bar 7 is formed with plane tongues 8 following upon each other and separated by spaces 9 which are relatively wide. These lifting bars are angularly bent along a line coincident with the base of the tongues 8 and the inner edge of the spaces 9, said inner edge having a straight extension in the longitudinal direction. The angle included by the tongues 8 and the continuous part of the lifting bars is preferably about 120, as in the embodiment illustrated (FIG. with some variation in both senses, for instance 110, but also other values are possible, for instance 90 (FIG. 7). Of importance is also the angle which the continuous part of the lifting bar 7 includes with the shell of the drum. Preferably the lifting bars 7 are mounted so as to have their continuous part disposed in a radial plane, as in the embodiment illustrated. Then, the tongues should extend nearly in the tangential direction (and in the sense of rotation), as the case is when the first-mentioned angle is 120, or exactly in the tangential direction, as the case is when the said angle is 90.

When the lifting bars 7 are shaped and arranged as stated above, each lifting bar 7 when moving upwards will first allow the falling-down of such material which is carried by the sections of the continuous part of the lifting bar opposite the spaces 9, as this material passes through the wide spaces 9, and later on when having passed the highest point the very same lifting bar will allow the falling-down of the material carried by the tongues 8 and the remaining sections of the lifting bar opposite the tongues. It might be assumed that the falling down or sliding down of the material carried by the lifting bars 7 will start about 45 before the highest point of the drum and will continue to above 45 after said highest point. Of course these values are dependent upon the nature of the material in question, and according to the invention the entire quantity of material carried by one lifting bar will never fall or slide down all at once. Anyhow the invention increases essentially the part of the cross-section of the drum that is filled with material freely falling down. Experiments have proved that practically the whole cross-section is filled with falling material.

According to FIGS. 1 and 3, the intermediate part of the length of the drum is provided with lifting bars 7 which are securely attached to the inside of the shell of the drum by suitable means, for instance angle pieces 10. In the right-hand end portion in FIG. 1 the lifting bars 7 are by means of end-rings 11 interconnected to a separate cage having an outer diameter smaller than the inner diameter of the shall of the drum and rolling freely in the drum while occupying an eccentric position in the drum; see the space S at the top in FIGS. 1 and 4. The effect of the invention, viz. the uniform distribution of falling material over the entire cross-section of the drum, is especially pronounced in connection with a freely rolling cage. Moreover, this construction is particularly adapted for the treatment of material of-sticky nature for securing that such material will not get stuck to the tongues and spaces of the lifting bars 7. Of course either one or the other of these two constructions can be utilized over the entire length of the drum. However, at the discharge end of the drum the lifting bars can be omitted so that the lifting bars extend from the charge end only to a point at a distance from the discharge end. Thus, a sector unit 12 can be provided in this free part of the drum instead of the omitted sections of the lifting bars, said sector unit allowing both heat-exchange and dust separation.

The sector unit comprising the channel-shaped sectors 12 and the longitudinally extending partitions 13 can be firmly mounted in the drum, as indicated in FIGS. 1 and 2. However, when a freely rolling cage is used, the sector unit is preferably connected with the freely rolling cage to form one unit therewith. For instance, as illustrated in FIGS. 8, 9 and 10, the radial walls of the sectors 12 are made with bar-shaped extensions 7', forming the lifting bars according to the invention and having interspaced tongues 8' at their inner edges, projecting in a nearly tangential direction, according to the invention.

Advantageously the lifting bars 7 or 7' can be utilized as supporting means for screw-like feeding bars which preferably are subdivided into separate smaller sections or feeding sheets 15 which extend obliquely each between two adjacent lifting bars and can be mounted in the spaces 9 or 9' between the tongues 8 or 8 on the lifting bars. Thus, said feeding sheets 15 attached to the lifting bars are spaced from the surrounding cylindrical surface of the shell of the drum, such spacing being relatively Wide. Thereby the advantage is attained that the sheets 15 will not feed until the charge has reached a certain level or amount in the drum. Then the feeding effect increases according to the increase of the charge.

Evidently the invention secures a very uniform action of the gaseous medium upon all parts of the charge as this passes through the drum while being recurrently lifted and allowed to fall down successively in a scattered distribution through the interior of the drum.

We claim:

1. An arrangement in a rotatable drum for treatment of a solid material in a fluent state by exchange of heat between the material and a gaseous medium, comprising lifting bars extending substantially longitudinally within the drum for lifting the material during rotation of the drum, the free edge of each lifting bar being formed with spaced-apart tongues of considerable width in the longitudinal direction at their free edges, the spaces between said tongues having an inner edge extending in the longitudinal direction, said tongues being bent in the direction of rotation and along a line substantially coincident with the inner edge of the spaces between the tongues, the bending angle of the tongues being such that the tongues extend substantially in a tangential direction, screw-like feeding bars being supported by the inner edges of said lifting bars.

2. An arrangement in a rotatable drum for treatment of a solid material in a fluent state by exchange of heat between the material and a gaseous medium, comprising lifting .bars extending substantially longitudinally within the drum for lifting the material during rotation of the drum, the free edge of each lifting bar being formed with spaced-apart tongues of considerable width in the longitudinal direction of their free edges, the spaces between said tongues having an inner edge extending in the longitudinal direction, said tongues being bent in.the direct-ion of rotation and along a line substantially coincident with the inner edge of the spaces between the tongues, the bending angle of the tongues being such that the tongues extend substantially in a tangential direction, screwlike feeding bars being supported by the inner edges of said lifting bars said feeding bars being subdivided into separate sections extending each between two adjacent lifting bars.

3. An arrangement in a rotatable drum for treatment of a solid material in a fluent state by exchange of heat between the material and a gaseous medium, comprising bar-like lifting members extending substantially longitudinal-1y within the drum for lifting the material during the rotation of the drum, said bar-like members being interconnected to form a separate cage having an outer diameter smaller than the inner diameter of the drum, said cage being adapted to roll freely in the rotating drum, the free edge of each lifting member being formed with spaced-apart tongues of considerable width in the longitudinal direction of their free edges, the spaces between said tongues having an inner edge extending in the longitudinal direction, said tongues being bent in the direction of rotation and along a line substantially coincident with the inner'ed-ge of the spaces between the tongues, the bending angle of the tongues being such that the tongues extend substantially in a tangential direction and screw-like feeding bars being supported by the lifting bars and spaced from the surrounding surface of the drum.

=4. An arrangement in a rotatable drum for treatment of Hi-So id m terial in ta-fluent state by exchange of heat between the material and a gaseous medium, comprising lifting bars extending substantially longitudinally within the drum for lifting the material during rotation of the drum, said lifting bars extending from the charge end of the drum to a point at a distance before the discharge end and being interconnected to form a separate cage having an outer diameter smaller than the inner diameter of the drum, said cage being adapted to roll freely in the rotating drum, a sector unit being provided in the drum between the discharge end and the cage in connection with the cage to form one rolling unit therewith, screw-like feeding bars being supported by the inner edges of said lifting bars, said feeding bars being subdivided into separate sections extending each between two adjacent lifting bars, the free edge of each lifting b-ar being formed with spaced-apart tongues of considerable width in the longitudinal direction of their free edges, the spaces between said tongues having an inner edge extending in the longitudinal direction, said tongues being bent in the direction of rotation and along a line substantially coincident with the inner edge of the spaces between the tongues, the bending angle of the tongues being such that the tongues extend substantially in a tangential direction.

References Cited by the Examiner UNITED STATES PATENTS WILLIAM F. ODEA, Primary Examiner.

NORMAN YUDKOFF, Examiner.

W. C, EVERETT, A. D. HERRMANN,

Assistant Examiners. 

4. AN ARRANGEMENT IN A ROTATABLE DRUM FOR TREATMENT OF A SOLID MATERIAL IN A FLUENT STATE BY EXCHABGE OF HEAT BETWEEN THE MATERIAL AND A GASEOUS MEDIUM, COMPRISING LIFTING BARS EXTENDING SUBSTANTIALLY LONGITUDINALLY WITHIN THE DRUM FOR LIFTING THE MATERIAL DURING ROTATION OF THE DRUM, SAID LIFTING BARS EXTENDING FROM THE CHARGE END OF THE DRUM TO A POINT AT A DISTANCE BEFORE THE DISCHARGE END AND BEING INTERCONNECTED TO FORM A SEPARATE CAGE HAVING AN OUTER DIAMETER SMALLER THAN THE INNER DIAMETER OF THE DRUM, SAID CAGE BEING ADAPTED TO ROLL FREELY IN THE ROTATING DRUM, A SECTOR UNIT BEING PROVIDED IN THE DRUM BETWEEN THE DISCHARGE END AND THE CAGE IN CONNECTION WITH THE CAGE TO FORM ONE ROLLING UNIT THEREWITH, SCREW-LIKE FEEDING BARS BEING SUPPORTED BY THE INNER EDGES OF SAID LIFTING BARS, SAID FEEDING BARS BEING SUBDIVIDED INTO SEPARATE SECTIONS EXTENDING EACH BETWEEN TWO ADJACENT LIFTING BARS, THE FREE EDGE OF EACH LIFTING BAR BEING FORMED WITH SPACED-APART TONGUES OF CONSIDERABLE WIDTH IN THE LONGITUDINAL DIRECTION OF THEIR FREE EDGES, THE SPACES BETWEEN SAID TONGUES HAVING AN INNER EDGE EXTENDING IN THE LONGITUDINAL DIRECTION, SAID TONGUES BEING BENT IN THE DIRECTION OF ROTATION AND ALONG A LINE SUBSTANTIALLY COINCIDENT WITH THE INNER EDGE OF THE SPACES BETWEEN THE TONGUES, THE BENDING ANGLE OF THE TONGUES BEING SUCH THAT THE TONGUES EXTEND SUBSTANTIALLY IN A TANGENTIAL DIRECTION. 